Content-type validation bypass via internal metadata flags
Published Mar 23, 2026 · Updated Mar 23, 2026
Metadata filtering failure in Rails Active Storage allows remote attackers to bypass content-type validation through direct uploads. DirectUploadsController persists client-supplied metadata without removing internal analyzed, identified, and composed flags, letting a client suppress automatic MIME identification and analysis. An application must expose direct uploads and rely on automatic identification; arbitrary content can then be submitted with a declared safe content type.
Summary
What happened
Metadata filtering failure in Rails Active Storage allows remote attackers to bypass content-type validation through direct uploads. DirectUploadsController persists client-supplied metadata without removing internal analyzed, identified, and composed flags, letting a client suppress automatic MIME identification and analysis. An application must expose direct uploads and rely on automatic identification; arbitrary content can then be submitted with a declared safe content type.
The record
- CVE
- CVE-2026-33173
- Published
- Mar 23, 2026
- Updated
- Mar 23, 2026
- Vendor
- Rails
- Product
- Active Storage
- Classifications
- CWE-925, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 23, 2026CVE publishedPublication date reported by the CVE source.
- Mar 23, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 7.2.3.1
- Affected versionversion=>= 8.0.0.beta1, < 8.0.4.1
- Affected versionversion=>= 8.1.0.beta1, < 8.1.2.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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